Electrosurgical tools have been available for many years which employ electrical energy to treat targeted patient tissue in various ways. For example, electrocauterization is utilized to seal off and close blood vessels during surgery to prevent blood loss. In addition, ablation is utilized to vaporize or remove tissue using electrical energy. Electrosurgical probes are typically designed to perform both of these functions, depending upon the type of power supplied thereto. Further, monopolar and bipolar electrosurgical tools have long been available, wherein monopolar tools direct electric current from an active electrode defined on the tool through the patient's body and to a return electrode, which return electrode is typically defined by a grounding pad attached to the patient. Bipolar tools, on the other hand, incorporate both an active and a return electrode directly into the tool.
Surgical procedures utilizing bipolar tools are often performed using a conductive irrigant, such as saline, for irrigation and for distending a joint, for example in orthopedic arthroscopic procedures. The conductivity of the saline solution provides a conduction pathway between the active and return electrodes of the tool. The delivery of a high-frequency current between the active and return electrodes effectively modifies tissue, and it is common for bubbles to form on the surface of the tool or probe tip which can interfere with the surgeon's view of the surgical site. This is particularly a problem when the electrosurgical tool is employed in an endoscopic surgical procedure, wherein the electrosurgical tool is inserted into the surgical site through a small opening or portal formed in the patient's body. The surgeon views the surgical site through an endoscope which is inserted into the surgical site through another portal. Thus, these bubbles are generated in the relatively small confines of the surgical site and cause significant problems for the surgeon in viewing the surgical site. Further, these bubbles are electrically and thermally insulating, and can inhibit the flow of new saline solution for rewetting the electrode. Consequently, the bubbles can cause undesirable reduction of current flow through the targeted tissue.
In order to address the undesirable bubble generation described above, some electrosurgical tools incorporate a suction feature into the tool to remove the bubbles. One type of electrosurgical tool manufactured by the Assignee hereof is capable of suction. More specifically, this tool includes an outer conductive shaft which is covered with an insulating material. The distal end of the shaft is exposed of the insulating material, and serves as a return electrode. The active electrode is disposed inside the outer shaft and is supported at the shaft tip by an insulator cap, typically constructed of ceramic. The insulator cap is mounted within the open distal end of the shaft, and defines therein two bores. The distal end of the active electrode extends through one of these bores, and a plastic suction tube extends inside and along the outer shaft and into the other bore. This arrangement thus permits a vacuum to be drawn through the tool from the distal end thereof.
Minimally invasive surgical techniques require surgical tools to be as small as possible in order to minimize trauma to the patient. As such, there is an ongoing effort to reduce the size of surgical instruments whenever possible. While the above tool works reasonably well for its intended purpose, the requirement for the outer shaft to house both a suction tube and wiring for delivering current to the active electrode presents difficulties in assembly of the tool. Further, this arrangement results in limited available space within the outer shaft, which places a limit on the diameter of a suction tube. In addition, the cap which insulates the active electrode from the return electrode is required to have multiple holes for accommodating the active electrode and suction tube, which makes it difficult to minimize the overall diameter of the insulator cap and thus the overall diameter of the tool tip.
Other conventional electrosurgical tools which are capable of suction include an elongate tubular member which defines a conduit therein for aspirating fluid and/or debris from the surgical site. This tubular member is constructed of a conductive material, and thus also functions as an energy-delivering electrode. For example, U.S. Pat. No. 5,520,685 discloses a suction coagulator defined by a tubular suction cannula covered with an insulating coating. The cannula has a distal end which is exposed of the insulating coating and defines the active electrode. An insulating sleeve is provided inside the distal end of the electrode portion of the cannula for preventing the formation of blood char. U.S. Pat. No. 3,974,833 also discloses an electrosurgical tool including a conductive suction tube which is exposed from insulating material at its distal end so as to define the active electrode. Further, U.S. Pat. No. 6,156,036 discloses an electrosurgical tool defined by inner and outer conductive tubes which are separated by an insulator. The innermost tube defines an aspiration conduit. Current is passed between the inner and outer tubes so as to boil surgical fluid located at the distal end of the tool.
The above devices advantageously incorporate a conductive tubular member which defines a conduit for fluid aspiration while simultaneously providing an electrically conductive pathway to the active electrode defined by the distal end of the tube. This structure eliminates the need for internal wiring for the electrode within the tool shaft. However, a disadvantage of the above devices is that they utilize the suction tube directly for delivery of electrical energy to the targeted tissue. That is, the electrode in the above devices is a monolithic component of the suction tube itself. Accordingly, the electrode is defined by the exposed ring-shaped distal end of the suction tube, and thus the electrode geometry is limited to the geometry of the suction tube. In an electrode having this ring-shaped geometry as defined by the exposed distal end of the suction tube, electrical flux is necessarily greatest at the periphery of the ring. However, the rate of fluid flow over this ring and into the suction passage of the suction tube can cause convective cooling at the periphery of the electrode, which can result in the inability to rapidly ablate tissue.
In order to obviate or at least minimize the disadvantages of the above devices, the instant invention is directed to an electrosurgical tool which incorporates a suction tube defining both a conduit for fluid aspiration and an electrically conductive pathway to an active electrode disposed at the distal end of the tool. The active electrode is initially formed as a separate component from the suction tube, and is joined to the distal end of the suction tube. The active electrode is preferably joined to the suction tube by a press or interference-fit, but may also be joined to the suction tube by crimping, welding, with a conductive adhesive, or by another suitable method. This structure advantageously allows more freedom in designing an electrode for optimizing energy delivery to the targeted tissue. Further, the electrode according to the invention includes a small hole which communicates with the suction conduit defined by the suction tube, which can minimize convective cooling at the periphery of the active electrode where electrical flux is greatest. The small suction hole defined in the active electrode can also help to prevent clogging downstream of the surgical site by minimizing the size of tissue fragments that enter the suction conduit.
Further, the tool according to the invention helps to resolve the spatial limitations of existing tools by eliminating the need for both a suction tube and electrode wiring to pass through the outer tool shaft and the insulator cap disposed at the distal end thereof, since a single tube serves both as a suction tube and as a conduit for delivering electrical energy to the electrode at the tip of the tool, and since only one passage must be defined through the insulator cap. As such, the internal diameter of the outer shaft can be significantly reduced, since no additional space is needed therein for electrode wiring. In addition, the diameter of the distal end of the tool can be reduced essentially to the size of the active electrode, plus the minimal ceramic thickness necessary for insulation purposes.
As an alternative to reducing the overall diameter of the tool shaft, the diameter in one embodiment can be kept identical to existing diameters, and the suction channel enlarged in order to increase flow rate. The instant invention thus maximizes the cross-sectional areas within the tool shaft by eliminating unused space therein. The concentricity of the return electrode defined by the outer shaft and the active electrode defined by the conductive suction tube allows the remainder of the available cross-sectional area to be essentially fully utilized by the suction channel, if desirable or necessary.
Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. The words “forwardly” and “distally” will refer to the direction toward the end of the arrangement which is closest to the patient, and the words “rearwardly” and “proximally” will refer to the direction away from the end of the arrangement which is furthest from the patient. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.